Pulmonary embolisms (PE) are a potentially lethal lung disease relating to clots in the pulmonary arteries. These clots hinder the passage of blood through the artery, which may result in an insufficient perfusion of the arterial vessel tree of the lung. The clots can be observed in high resolution CT volume images, because the absence of contrast agent in the clots results in lower Hounsfield values.
“A novel method for pulmonary emboli visualization from high-resolution CT images”, by Pichon, Novak, Kiraly, and Naidich, in Proc. SPIE Medical Imaging 2004, describes a method to highlight potential PEs on a 3D representation of the pulmonary arterial tree. First lung vessels are segmented using mathematical morphology techniques. The density values inside the vessels are then used to color the outside of a shaded surface display of the vessel tree. As PEs are clots of significantly lower Hounsfield unit values than surrounding contrast-enhanced blood, they appear as salient contrasted patches in this 3D rendering.
“Analysis of arterial sub-trees affected by pulmonary emboli”, by Kiraly, Pichon, Naidich, and Novak, in Proc. SPIE Medical Imaging 2004, proposes a method to compute characteristics of the local arterial tree given the location of a PE. The computed information localizes the portion of the arterial tree that is affected by the embolism. The method is based on the segmentation of the arteries and veins followed by a localized tree computation at the given site. The method determines bifurcation points and the remaining arterial tree. The document also discloses assessing the affected lung volume and arterial supply.